Implantation or something else?

I have been off of the depo shot for approximately 3 months (was due to get it in Jan). In that time I have not had a period of any kind and have been having unprotected sex in hope of getting pregnant. A couple of days ago I started having very light spotting, a brownish color and also light brown as well as a little bit of cramping on my right side. This has been going on for 2 and a half days. Is it possible that it could be implantation and that I could be pregnant or am I completely crazy? Anyone with advice please please help!